Madhab Roy

A study on ferroresonance and its depedence on instant of switching angle of the source voltage

The instant of switching on ac supply voltage plays an important role in formation of ferroresonance. Simulation of ferroresonance is worked out on each electrical degree over 0° to 360° of the sinusoidal supply voltage with varying magnitude of initial magnetization. The resulting ferroresonance over-voltages, currents are presented and analyzed identifying critical features.

A study on ferroresonance with a varying initial conditions using a nonlinear model of transformer

Ferroresonance is a nonlinear oscillatory phenomenon, which occurs in capacitance-coupled transformers under certain conditions in a power system. The magnetizing branch of the transformer at no-load is modelled by nonlinear equation using a laboratory recorded hysteresis loop of a transformer. Various numerical simulations of ferroresonance are performed when source voltage are treated as parameter at different initial magnetization. The power spectral density and phase-plane analyses are conducted on ferroresonance over-voltage generated across transformer and line capacitance. Ferroresonance current, flux and their inter relationship are presented.

Structural and Optical Properties of V2O5-MoO3-ZnO Glass-Nanocomposite System

ABSTRACT The present work points to highlight the physical, structural and the optical properties of some semiconducting V2O5-MoO3-ZnO glass-nanocomposites using density, molar volume, X-ray diffraction (XRD), field effect scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and UV-VIS absorption spectra. We have observed that addition of V2O5 increases (or decreases) the density (or molar volume) of the glassy system due to structural changes. Distribution of Zn3V2MoO11, Zn2.5VMoO8 and Zn2V2O7 nanoparticles has been confirmed from FESEM and XRD studies. It has been observed from FTIR spectra that the network structure depends upon isolated strongly deformed M oO4 polyhedra and VO4 metavanadate chains. Vibrations of MoO6 octahedra, Zn2V2O6, Zn2V2O7, Zn3V2MoO11 and VO2 are observed from the Raman spectroscopic studies. The fundamental UV-VIS absorption spectra have been analyzed, which indicates indirect transitions. GRAPHICAL ABSTRACT

Analysis of Ferroresonant Oscillations in a Nonlinear Circuit

Ferroresonance is a nonlinear oscillatory phenomenon, which occurs in capacitively coupled transformers under certain conditions in a power system. The magnetizing branch of the transformer at no-load is modeled by nonlinear equation. The coupling capacitances are treated as parameters and different numerical simulations of ferroresonance are performed. The power spectral density and phase plane analyses are conducted on ferroresonance over-voltage generated across transformer to identify the modes of ferroresonance.

V 2 O 5 -MoO 3 -ZnO thick film resistors as highly selective trace level ethanol gas sensors

The Glass nanocomposite materials in the form of fine granular powders were synthesized by conventional melt quenching technique. Thick films of the synthesized powders were fabricated by screen printing technique, followed by firing at 100oC, for 2 hours. Upon exposure to 50 ppm ethanol gas, due to oxidation or reduction reaction at the surface of the as prepared nanocomposite materials with the target gas, exchange of electrons take place thereby affecting the sensors resistance greatly leading to drastic change in conductance. The glass nanocomposite of composition xV2O5-(1−x) (0.05MoO3-0.95ZnO) where x = 0.95 (sample-C) was observed to most sensitive to ethanol at room temperature. The surface misfits, operating temperature, gas concentrations, etc. affect the microstructure and gas sensing performance of the sensing element. The quick response and fast recovery are the main features of this sensor. The microstructure of the as prepared glass nanocomposites was analyzed to study the gas response and selectivity of the sensor in the presence of ethanol and some other gases also.